Monitoring and controlling unit operations

Abstract

Fluid sensor methods and systems adapted for monitoring and / or controlling distillation operations in fluidic systems, such as batch distillation operations or continuous distillation operations, are disclosed. Preferred embodiments are directed to process monitoring and / or process control for unit operations involving endpoint determination of a distillation, for example, as applied to a liquid-component-switching operation (e.g., a solvent switching operation), a liquid-liquid separation operation, a solute concentration operation, a dispersed-phase concentration operation, among others.

Description

BACKGROUND OF THE INVENTION [0001] The present invention generally relates to the field of fluid sensors and methods, and more particularly to the field of fluid sensors and methods for sensing fluids in unit operations involving separation, especially unit operations involving distillation, evaporation, extraction, drying and / or chemical reaction. Such fluid sensors and methods are suitable for use in process monitoring and / or process control systems and / or operations, and may be especially suitable for example, in the application of Process Analytical Technologies. The present invention relates, in preferred embodiments, to fluid sensor devices and methods adapted for monitoring and / or controlling distillation operations in fluid process systems, such as batch distillation operations or continuous distillation operations. The present invention relates, in particularly preferred embodiments, to process monitoring and / or process control, including devices and methods, for unit opera...

AI Technical Summary

Benefits of technology

[0247] The size of the sensing elements, especially mechanical resonator sensing elements such as flexural resonator sensing elements is not critical to the invention. In some applications, however, it should be appreciated that one advantage of the present invention is the ability to fabricate a very small sensor using the present resonators. For example, one preferred resonator has its largest dimension smaller than about 2 cm, and more preferably smaller than about 1 cm. One resonator has length and width dimensions of about 3 mm by 8 mm, and possibly as small as about 1 mm by 2.5 mm. Geometry of the resonator may be varied as desired also. For example, the aspect ratio of tines of the tuning forks, or geometrical factors of other resonators can be optimized in order to achieve better sensitivity to the properties of the gas phase, liquid phase or its particular components (e.g., a lubricant). For example, the aspect ratio of a tuning fork tine may range from about 30:1 to about 1:1. More specifically, it may range from about 15:1 to about 2:1.

[0248] It is thus seen that a preferred resonator is configured for movement of a body through a fluid. Thus, for example, as seen in FIG. 4B, the resonator may have a base and one or a plurality of tines projecting from the base. It is preferred in one aspect that any tine has at least one free tip that is capable of displacement in a fluid relative to the base. FIG. 4C illustrates a cantilever 1220 having a base 1240 and a free tip 1260. Other possible structures, seen in FIGS. 4D and 4E contemplate having a disk 1280, a plate 1300 or the like that is adapted so that one portion of it is displaceable relative to one or more variable or fixed locations 1320 (1320′). As seen in FIG. 4F, in yet another embodiment a resonator 1340 is contemplated in which a shear surface 1360 of the resonator has one or more projections 1380 of a suitable configuration, in order that the resonator may be operated in shear while still functioning consistent with the flexural or torsional resonators of the present invention, by passing the projections through a fluid.

[0249] In still other embodiments, and referring to FIG. 4G, 4H and 4I, it is contemplated that a resonator 2000 may include an elongated member 2020 supported on its sides 2040 by a pair of arms 2060. As shown respectively in FIGS. 4G through 4I, the elongated member may be configured to oscillate side-to-side, back and forth, in twisting motions or combinations thereof.

[0250] The flexural resonator, such as the embodiment of FIG. 4B, may be constructed as a monolithic device. Yet another structure of the present invention contemplates the employment of a laminate or other multi-layer body that employs dissimilar materials in each of at least a first layer and a second layer, or a laminate comprised of layers of piezoelectric material of different orientations or configurations. According to this approach, upon subjecting one or more of the layers to a stimulus such as temperature change, an electrical signal or other stimulus, one of the materials will respond differently from the other and the differences in responses will, in turn, result in the flexure of the resonator. In yet another embodiment, it is contemplated that plural resonators can be assembled together with an electrode at least partially sandwiched therebetween. In this manner, it may be possible to further protect electrodes from harsh conditions, while still achieving the desired flexure. One specific example might include a two or more lithium niobate or quartz tuning forks joined together with a gold electrode therebetween. Other configurations (e.g., an H-shaped resonator) and material combinations may be employed as well, as disclosed in U.S. Provisional Application Ser. Nos. 60 / 456,767 and 60 / 456,517 (both filed Mar. 21, 2003), incorporated by reference.

[0251] As can be seen, the selection of the specific resonator material, structure, or other characteristic commonly varies depending upon the specific intended application. Nonetheless, it is preferred that for each application, the resonator is such that one or a combination of the following features (and in one highly preferred embodiment, a combination of all features) is present: a coating, if placed upon the resonator in a thickness greater than about 0.1 micron, will not substantially detract from resonance performance; the resonator is operable and is operated at a frequency of less than about 1 MHz, and more preferably less than about 100 kHz; the resonator is substantially resistant to contaminants proximate to the sensor surface; the resonator operates to displace at least a portion of its body through a fluid; or the resonator responses are capable of de-convolution for measuring one or more individual properties of density, viscosity, viscosity / density product, conductivity or dielectric constant.

[0252] The resonator may be uncoated or coated or otherwise surface treated over some or all of its exterior surface. A preferred coating is a metal (e.g., a conductive metal similar to what may be employed for electrodes for the sensor, such as silver, gold, copper, aluminum or the like), plastic, ceramic or composite thereof, in which the coating material is substantially resistant to degradation from the fluid to which it is to be exposed or to surface build-up, over a broad temperature range. For example, one preferred embodiment, contemplates the employment of a base resonator material and a performance-tuning material. Among the preferred characteristics of the resonators of the present invention is the base material is generally thermally stable. For example, in one preferred embodiment, the material exhibits a dielectric constant that is substantially constant over a temperature range of about 0° C. to about 100° C., more preferably about −20° C. to about 150° C., and still more preferably about −40° C. to about 200° C. For example, it is contemplated that a preferred material exhibits stability to a temperature of at least about 300° C., and more preferably at least about 450° C. In another aspect, the dielectric constant of the performance-tuning material preferably is greater than that of quartz alone, such as by a factor of 5 or more, more preferably by a factor of 10 or more and still more preferably by a factor of 20 or more.

Problems solved by technology

In certain operations, such sampling steps can add potentially 2-3 hours or more onto the batch timecycle.

Similar issues are encountered in monitoring and controlling various other fluid process operations, including liquid / liquid extraction, liquid / solid extraction, evaporation, drying and various chemical reactions.

Control issues arise in the operation of both batch and continuous processes.

Reaction control presents unique problems in the case of polymerization reactions.

Other and somewhat differing issues are presented in the formation of lower molecular weight products, e.g., in chemical or pharmaceutical manufacturing operations.

Control problems are confronted in both batch and continuous processes.

However, because these techniques require substantial capital investment, extensive calibration models, and relatively expensive maintenance, they are difficult to apply in relatively complex operations, especially where there are plural phases in a sample (e.g., in slurry processing where sample handling devices may become plugged with solids), and are difficult to justify in relatively simple operations such as solvent switch wherein at least rough approximations of distillation end points may be determined by monitoring head pressure, overhead vapor temperature and / or still pot temperature.

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